Here's the thing, grandma may simply be closer to one child than the other, but showing "favortism" is not acceptable. However, and please take no offense to this, could your perception of the situation perhaps contribute to the problem? I say this as a parent I have been in a similar situation. While some grandparents and other family members do play favorites, sometimes I would find that my awareness of it was more heightened than the child's. After a long hard look, I realized that although my youngest was closer to my mother than the oldest, she wasn't so much showing favortism as she was trying to help meet their needs as individuals. Sometimes one child is needier than another, and this goes back and forth. However, if this is not the case and it is blatant favortism, don't say anything to your children unless they broach the subject or are obviously upset. Take it up with grandma before the situation approaches in a non confrontational way. "Little whatever his name is was really upset that and....., could you maybe.....whatever you feel would help the situation. Go on to explain that they and you love her dearly but intentional or not, her actions are hurting the other child. If you need to talk to your children, do it in such a manner where nothing is ill spoken of grandma and the child does not feel as though they are to blame. These situations can be really tough but only you know your children and know how to comfort them.